The high number of leak events that took place in recent years at a 25.4 cm (10”)Øpipeline transporting anhydrous liquid ammonia, located in the Southeast of Mexico, was the main reason to carry out a numb...The high number of leak events that took place in recent years at a 25.4 cm (10”)Øpipeline transporting anhydrous liquid ammonia, located in the Southeast of Mexico, was the main reason to carry out a number of field studies and laboratory tests that helped establish not only the failure causes but also mitigation and control solutions. The performed activities included direct evaluation at failure sites, total repair programs, metallographic studies and pipeline flexibility analyses. The obtained results were useful to conclude that the failures obeyed a cracking mechanism by Stress Corrosion Cracking (SCC) which was caused by the combined effect of different factors: high stress resistance, high hardness of the base metal with a microstructure prone to brittleness and residual strains originated during the pipeline construction. From the operative, logistic and financial standpoints, it is not feasible to release the stress of approximately 22 km of pipeline. Therefore, the only viable solution is to install a new pipeline with suitable fabrication, construction and installation specifications aimed at preventing the SCC phenomenon.展开更多
Semiconductor molecular films based on a gallium phthalocyanine chloride (GaPcCl) and a bidentate amine were prepared by using vacuum thermal evaporation and electrochemical techniques in order to investigate the pref...Semiconductor molecular films based on a gallium phthalocyanine chloride (GaPcCl) and a bidentate amine were prepared by using vacuum thermal evaporation and electrochemical techniques in order to investigate the preferred conduction paths within the films. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were employed to characterize the morphology of the films. The conductivity measurements were performed with two different methods in order to investigate preferential conduction directions. The film transverse conductivity was obtained by using scanning tunneling spectroscopy (STS) and the in-plane film conductivity was measured with a four-point probe system. From spectroscopy measurements, the tunneling conductance (dI/dV) was also obtained. From these results, it was found that the conductive nature of the films was strongly influenced by the deposition technique which in turn defined the morphological characteristics of the film. The evaporated method showed better conductivity response and provided semiconductor characteristics in the film transverse direction with an in-plane ohmic response. Finally, contact angle measurements were performed and showed hydrophobic characteristics in all cases.展开更多
文摘The high number of leak events that took place in recent years at a 25.4 cm (10”)Øpipeline transporting anhydrous liquid ammonia, located in the Southeast of Mexico, was the main reason to carry out a number of field studies and laboratory tests that helped establish not only the failure causes but also mitigation and control solutions. The performed activities included direct evaluation at failure sites, total repair programs, metallographic studies and pipeline flexibility analyses. The obtained results were useful to conclude that the failures obeyed a cracking mechanism by Stress Corrosion Cracking (SCC) which was caused by the combined effect of different factors: high stress resistance, high hardness of the base metal with a microstructure prone to brittleness and residual strains originated during the pipeline construction. From the operative, logistic and financial standpoints, it is not feasible to release the stress of approximately 22 km of pipeline. Therefore, the only viable solution is to install a new pipeline with suitable fabrication, construction and installation specifications aimed at preventing the SCC phenomenon.
文摘Semiconductor molecular films based on a gallium phthalocyanine chloride (GaPcCl) and a bidentate amine were prepared by using vacuum thermal evaporation and electrochemical techniques in order to investigate the preferred conduction paths within the films. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were employed to characterize the morphology of the films. The conductivity measurements were performed with two different methods in order to investigate preferential conduction directions. The film transverse conductivity was obtained by using scanning tunneling spectroscopy (STS) and the in-plane film conductivity was measured with a four-point probe system. From spectroscopy measurements, the tunneling conductance (dI/dV) was also obtained. From these results, it was found that the conductive nature of the films was strongly influenced by the deposition technique which in turn defined the morphological characteristics of the film. The evaporated method showed better conductivity response and provided semiconductor characteristics in the film transverse direction with an in-plane ohmic response. Finally, contact angle measurements were performed and showed hydrophobic characteristics in all cases.
